User interface device

ABSTRACT

A user interface device for controlling a robot manipulator having an end effector comprising at least one movable element, the user interface device comprising: a body for being held by a user, the body comprising an elongate grip portion configured to be gripped by one or more of a user&#39;s second to fourth fingers; a trigger extending transversely to the direction of elongation of the grip portion, the trigger being supported by the body so as to be capable of rotating relative to the body about a rotation axis passing through the grip portion; and a drive mechanism at least partially housed in the grip portion, the drive mechanism being coupled to the trigger for applying a torque to the trigger.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of and claims priority to U.S.application Ser. No. 17/060,668 filed on Oct. 1, 2020, which is acontinuation and claims priority to U.S. application Ser. No. 16/334,873filed on Mar. 20, 2019, which is a national phase application ofPCT/GB2017/052786 filed on Sept. 19, 2017, which claims the benefit ofGreat Britain Patent Application No. 2016/16086, filed on Sept. 21,2016. The forgoing applications are herein incorporated by reference infull.

TECHNICAL FIELD

This invention relates to user interface devices for controlling roboticsystems such as master-slave manipulators.

SUMMARY

A common task for a user interface device is to control the movement ofan object in two or three dimensions. The object could be a real object,or a virtual object such as a character in a game or a simulatedvehicle. A convenient manifestation for a device like this is a sculptedform which is shaped so as to fit naturally into one or both of a user'shands. Such a device can carry a series of buttons by means of which theuser can provide input. Additionally, the device can containaccelerometers allowing the user to provide input by moving the deviceitself. Devices of this type are common as controllers for gamesconsoles. Examples include the Microsoft Xbox controllers, the NintendoWii Remote and Wii Nunchuck, the Sony DualShock PlayStation controllersand the Sony Move controller. FIG. 1 shows schematically an example ofsuch a controller. The controller of FIG. 1 comprises a sculpted casing1. The side edges 2 of the casing are curved so as to fit naturally intothe palms of both of a user's hands at the same time. The lateralportions 3 of the casing extend rearwardly beyond the central portion 4of the casing. This allows the more ulnar of the user's fingers toextend around the rear portions, helping the user to hold the devicesecurely. The central part 4 of the casing carries a number of inputbuttons 5 which can be accessed by the thumbs of a user holding thecontroller in the normal way.

Ergonomic considerations are of great importance in designingcontrollers of this type. Some preferred characteristics are:

-   -   the shape of the controller should be comfortable for users of        different hand sizes to hold;    -   the buttons should be easily reached when a user is holding the        device in the intended way;    -   the shape of the device should indicate intuitively to a user        how the device is to be held.

It is preferred that these features are particularly optimised fordevices of this type because they could be used continuously for longperiods of time. A significant factor in the ergonomic design ofcontrollers of this type is that their weight is borne by the hands ofthe user. This affects the muscle loading in the user's forearms inparticular, which influences the shapes that a user will findcomfortable and the movements that could cause strain.

FIG. 2 shows a known controller for a master-slave manipulator having anend effector that comprises a pair of movable jaws. The controller has aprimary input stern 10. The primary input stern constitutes the distalend of a gimbal system 11 which permits the primary input stern to bemoved with three degrees of rotational freedom. The proximal end of thegimbal system is attached to a base by a parallelogram system, part ofwhich is shown at 12, which permits the primary input stern to be movedwith three degrees of translational freedom with respect to the base.The primary input stern is provided with two rotatable elements 13, 14which can be bound by loops 15 to an operator's fingers. The operatorcan move the primary input stern 10 with six degrees of freedom tocommand a change in position of the end effector, and can move theelements 13, 14 to command opening or closing of the jaws of the endeffector. One difficulty with an input device of this type is that itcan be tiring to use if the user's forearms are not supported. A restcan be provided for the user's forearms, but that restricts the workingpositions the user can adopt.

There is a need for an improved design of input device, for example onethat is more comfortable to use than prior designs.

According to the present invention there is provided a user interfacedevice for controlling a robot manipulator having an end effectorcomprising at least one movable element, the user interface devicecomprising: a body for being held by a user, the body comprising anelongate grip portion configured to be gripped by one or more of auser's second to fourth fingers; a trigger extending transversely to thedirection of elongation of the grip portion, the trigger being supportedby the body so as to be capable of rotating relative to the body about arotation axis passing through the grip portion; and a drive mechanism atleast partially housed in the grip portion, the drive mechanism beingcoupled to the trigger for applying a torque to the trigger.

The body may be configured to be gripped in normal use by a single handof the user.

The body may comprise a head portion attached to the grip portion. Thehead portion may be located so as to lie alongside the trigger.

The head portion may define a recess on the side thereof opposite thetrigger, the recess being configured for receiving the thumb of a usergripping the grip portion.

The trigger may be located relative to the grip portion for engagementby the first finger of a user gripping the grip portion.

The drive mechanism may comprise a motor. The motor may be arranged forapplying force to the trigger. The majority of the volume of the motormay be located within the grip portion. The trigger may be arranged torotate relative to the body about a rotation axis. The rotation axis maybe parallel with and optionally coaxial with the rotation axis of themotor.

The drive mechanism may comprise a gearbox. The majority of the volumeof the gearbox may be located within the grip portion.

The drive mechanism may terminate in a drive shaft. The drive shaft maybe coincident with the rotation axis of the trigger. The trigger may becarried by the drive shaft. The drive mechanism may be configured forapplying a torque to the trigger through the drive shaft.

The grip portion may have an axis of elongation. The grip portion maysatisfy one or both of the criteria: (i) a minimum circumferenceperpendicular to that axis of 40 mm and (ii) a maximum circumferenceperpendicular to that axis of 160 mm.

The length of the grip portion along the axis of elongation may begreater than 50 mm.

The user interface device may comprise a position sensor for sensing theposition of the trigger relative to the body.

The user interface device may comprise a force sensor for sensing forceapplied between the trigger and the body.

According to a second aspect of the invention there is provided arobotic manipulator system comprising: a user interface device as setout above; a robot manipulator comprising at least one sensor; and acontrol unit configured to control the drive unit to provide forcefeedback by means of the trigger to a user of the user interface devicein dependence on a signal received from the sensor.

The sensor may be a force sensor configured to detect a force applied toa part of an end effector carried by the robot manipulator.

The end effector may be an end effector of a surgical instrument carriedby the robot manipulator.

The control unit may be configured to control the motion of a part ofthe robot manipulator in dependence on input received from the sensor orone of the sensors of the user interface device.

The control unit may be configured to control the motion of the part ofthe end effector in dependence on input received from the sensor or oneof the sensors of the user interface device.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described by way of example withreference to the accompanying drawings. In the drawings:

FIG. 1 shows a game controller.

FIG. 2 shows one form of controller for a master-slave manipulator.

FIG. 3 shows a control device from the front (FIG. 3 a ), the left side(FIG. 3 b ), behind (FIG. 3 c ), the right side (FIG. 3 d ), above (FIG.3 e ) and below (FIG. 3 f ).

FIG. 4 is an oblique view of the control device of FIG. 3 above, leftand in front.

FIG. 5 shows a robotic manipulator system.

FIG. 6 is a partial cross-section through the controller of FIG. 3 .

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

The control device 20 of FIGS. 3 and 4 is designed to be held in auser's hand for providing (i) three-dimensional motion input bytranslation and rotation of the body 21 of the control device and (ii)functional input in dependence on the position of the trigger lever 22relative to the body of the control device.

For ease of explanation the controller will be described with referenceto mutually orthogonal X, Y and Z axes indicated in FIGS. 3 a and 3 b .The X axis is the forward/rearward axis of the controller. The Y axis isthe left/right axis of the controller. The Z axis is the up/down axis ofthe controller.

In this example the control device is intended to be grasped in theright hand. A mirror image control device could be intended for the lefthand. The body 21 of the control device has a head 23 and a grip 24. Thegrip 24 sits in the palm of the user's hand 40. The user's second tofourth fingers 41 are wrapped around the grip. The user's first/indexfinger 42 is placed on the input lever or trigger 22. The user's thumb43 is placed on the opposite side of the head to the input lever. Useracceptance testing of devices of this type has established that manyusers naturally pick up and hold such a device in this manner, withtheir wrist in a neutral position and their thumb opposing their finger.This has the result that for three-dimensional motion input the user'swrist is free to move in flexion, extension, adduction and abduction;and that when the user depresses the input lever 22 towards the body 21of the control device it is by a pinching action between the user'sthumb 43 and index finger 42, that can help to stabilise the user's hand40 in relation to the body of the controller when the lever is beingpositioned.

The grip 24 may be of any convenient shape: for example of generallycylindrical form. It may have a circular, elliptical, square orirregular cross-section. The grip could be configured to be gripped byone, two or three fingers, but it is preferred that it is configured tobe gripped by three fingers since that helps the controller to be heldfirmly and comfortably. It is preferably configured to be gripped by themore ulnar of the user's fingers. Different controllers could beprovided for hands of different sizes, but for many users a grip havinga circumference of between 80 mm and 180 mm over a length of between 60mm and 150 mm can be comfortable. The grip could incorporate ribs on itsfront surface, the ribs defining channels between them to cup the user'sfingers when the controller is being held. This can improve comfort andhelp to stabilise the controller for rotations involving pronation orsupination of the user's wrist. The grip is slimmer than the head. Incross-section perpendicular to the extent of the grip, the grip may begenerally circular. For example, the shape of the grip may be such thatin all cross-sections perpendicular to the length of the grip, themaximum width of the grip in that cross-section is not more than 30%greater than the depth of the grip in that cross-section.

The head 23 is rigidly attached to the palm grip. The head and the palmgrip may be parts of a common housing. The head extends forwardly of thegrip. The length of the head in the X direction may, for example be inthe range from 50 to 150 mm. This provides sufficient space for a userto align their first finger along the side of the head without the headbeing overly bulky. Also, if the head is sized in that way, to be of asimilar scale to the user's hand, the fact that the head extends in theX direction provides the user with a visual cue to hold their indexfinger along the side of the head.

Along the right lateral face of the head is the trigger lever 22. Thetrigger lever is mounted on the head so that it can rotate relative tothe head about an axis, e.g. one of axes 25 a, 25 b (see FIGS. 3 d and 3e ). In the case of axis 25 a, the axis extends generally through thegrip portion 24. It extends generally along the elongation direction ofthe grip portion. In the case of axis 25 b the axis 25 is aligned withthe Z axis of the controller. The trigger extends forward of therotation axis 25 a/25 b. The forward end 27 of the trigger is remotefrom the rotation axis. The forward end of the trigger can be engaged bythe first finger of a user of the controller, when the controller isheld as intended, so that the user can press the forward end of thetrigger into the head by flexion of the first finger. The length of thetrigger is preferably such that the distance between the rotation axisof the trigger and the forward-most outer-facing point of the trigger isin the range from 40 mm to 120 mm. The trigger is resiliently biasedaway from the central X-Z plane of the head, for example by a leaf orcoil spring 26 acting between the head and the trigger. In its restingposition the trigger extends out of the profile of the head, as shown inFIG. 3 d . A gap is left between the free end of the trigger and thehead of the controller when the trigger is in its resting position.Locating the trigger in this way can provide a visual cue for the userto rest their first finger on the trigger when first picking up thecontroller. The forward end of the trigger may be located in front ofthe forward end of the head. Alternatively, the forward end of the headmay be located in front of the forward end of the trigger

Axis 25 b has the potential advantage that when the controller is beingheld as intended by a user, the axis may be substantially parallel tothe movement axis of the carpal-metacarpal joint of the first finger ofthe user's hand on the controller. However, axis 25 a has otheradvantages, as will be discussed further below.

The trigger could be articulated in other ways. For example, it couldmove linearly: it could be a push-button located near the forward end ofthe head. Alternatively, it could be a touch-sensitive panel that isattached to the exterior of the head. Instead of extending out of theprofile of the head the trigger could remain within the profile of thehead, whilst being exposed to the exterior of the head so it can beengaged by a user's finger. Instead of being resiliently biased thetrigger could be provided with a finger loop that allows a user to moveit under extension of the first finger.

A position sensor is provided within the head to sense the position ofthe trigger relative to the head. The position sensor could senseposition on a binary basis: it could simply discriminate betweenrelatively outward and relatively inward positions of the trigger. Morepreferably the sensor can discriminate a range of positions of thetrigger, allowing it to indicate more precisely the extent to which thetrigger is pressed. The position sensor could be a rotational encoder ora potentiometer arranged about the rotation axis of the trigger. Inaddition to or instead of a position sensor the controller couldcomprise a force and/or torque sensor for detecting the force applied tothe trigger and/or the torque applied to the trigger about axis 25.

When the controller is held as intended the user's thumb 43 extendsalong the opposite side of the controller to the trigger. This allowsthe user's thumb 43 to oppose motion of the trigger under the action ofthe user's index finger 42. In practice, it is often not necessary forthe user to exert force with their thumb 43 to oppose the index fingerflexion. However, it has been found that the ability to exert forces onthe parts at both sides of the trigger joint can allow users to move thetrigger with more precision. It can also help to stabilise thecontroller in a user's hand 40. A recess 28 along the upper left side ofthe head accommodates the user's thumb 43.

Additional user interface input devices can be provided on the exteriorof the head. For example, there could be one or more push-buttons,rotational knobs, joysticks, rocker switches or the like. Conveniently,these can be disposed in the region of the head that is accessible to auser's thumb when their hand is in position on the controller. That isgenerally the upper left side of the controller in the case of aright-handed controller. One or more input devices could be located onor near the trigger 22, for actuation by the user's first finger. One ormore input devices could be located on or near the trigger 22, foractuation by the user's other fingers. If the grip 24 is configured tobe gripped by fewer than three fingers then one or more input devicesconvenient for those fingers could be located on the lower parts of thehead. Input devices such as buttons, joysticks and rocker switches maybe located on the upper face of the head.

In summary, when a user is correctly holding the controller of FIG. 3 intheir right hand 40:

-   -   i. One or more of their fifth to second fingers 41 wrap around        the grip 24. This stabilises the controller relative to the        user's hand 40.    -   ii. The user's first finger 42 extends along the right flank of        the head of the controller for applying a leftward force against        the trigger 22.    -   iii. The user's thumb 43 extends along the left flank of the        head of the controller. The user's thumb 43 being in this        position can help the user to make more precise movements of the        trigger. Also, further user interface input devices can be        positioned for activation by the user's thumb 43.

The rear of the head of the controller is continuous with the rear ofthe grip. The front of the head of the controller extends in front ofthe most forward part of the grip. The head of the controller isattached to the top of the grip. The head does not extend below the topof the grip. The grip extends downwardly from the head. Otherconfigurations are possible.

The controller of FIG. 3 is intended to be used as an input device forcontrolling a robot manipulator. The robot manipulator may be as shownin FIG. 5 . The robot manipulator of FIG. 5 has an arm 30 which extendsfrom a base 31. The arm is articulated by a series of revolute jointsalong its length. At the distal end of the arm is an instrument 32 whichterminates in an end effector. In this example the end effector has apair of opposed jaws 33. These can be moved relative to each other togrip or cut objects located between the jaws. The jaws can be driven tomove by a drive motor 34 at the distal end of the arm. The drive motoris coupled to the jaws by cables extending along the interior of theinstrument's shaft. The robot is governed by a control unit 35. Thecontrol unit receives inputs from the controller 20 of FIG. 3 and fromother sources such as motion linkage 36 and arm position/force sensors37.

Motion linkage 36 is an articulated linkage which supports thecontroller 20 and permits it to be moved with six degrees of freedom.The configuration of the motion linkage can be detected by sensors onthe linkage and passed to the control unit 35. In that way movement ofthe controller 20 can be used to control the movement of the arm.Instead of the motion linkage 36, the controller 20 could be equippedwith accelerometers which permit its position and orientation to beestimated.

The control unit comprises a processor 38 which executes code stored ina non-transient form in a memory 39. On executing the code the processordetermines a set of signals for commanding movement of the joints of therobot, and for moving the jaws 33 of the instrument in dependence on theinputs from the controller, the motion linkage and the armposition/force sensors. The code is configured so that the motion of therobot is essentially dictated by the inputs from the controller and themotion linkage. For example, in a normal operating mode (i) the attitudeof the end effector may be set by the attitude of the controller aboutits rotational degrees of freedom; (ii) the position of the end effectormay be set by the position of the controller about its translationaldegrees of freedom; and (iii) the configuration of the jaws may be setby the position of the trigger 22 relative to the body 21.

FIG. 6 shows a partial cross-section through the controller of FIG. 3 .In FIG. 6 the body of the controller is sectioned on the X-Z plane andthe trigger 22 is shown in full.

In FIG. 6 the rotation axis of the trigger is 25 a. Axis 25 runs throughthe grip portion 24. Inside the grip portion 24 is an electric motor 50which drives a gearbox 51. The output shaft 52 of the gearbox serves asa pivot for the trigger about axis 25 a. The rotation axis of the outputshaft 52 is coincident with the rotation axis 25 a. The trigger isfixedly attached to the output shaft 52. A torque sensor 53 senses thetorque between the trigger and the output shaft. A position sensor 54senses the position of the output shaft. The outputs of the sensors 53,54 pass to the control unit 35. The control unit 35 provides a drivesignal to the motor 50. The gear ratio of the gearbox may be in therange from 10:1 to 25:1, but other ratios are also possible. The gearboxmay be omitted if the motor itself has a suitable rating. The trigger isattached directly to, and carried by, the output shaft of the gearbox orof the motor if the gearbox is omitted. The motor may comprise a rotorand a stator. The motor may have a rotation axis: i.e. the axis aboutwhich the rotor rotates with respect to the stator. The rotation axis ofthe trigger may be parallel with and more preferably coincident with therotation axis of the motor. That allows for efficient packaging of themotor in the controller, without a need for complex linkages to transferdrive across to the trigger.

The system may operate in various ways to provide a command signal tothe drive motor 34 which drives the jaws. In a position authority modethe jaws are driven towards a position that maps on to the position ofthe trigger 22 relative to the head 21, as sensed by position sensor 54.In a force authority mode the jaws are driven so as to apply a forcethat maps on to the force applied to the trigger 22 relative to the head21, as sensed by force sensor 53. Combinations of these modes are alsopossible.

The motor 50 is used to provide force feedback (which encompasses torquefeedback) to a user of the controller. The amount of force feedback tobe provided can be determined by the control unit using a predeterminedalgorithm. For example, the amount of force to be provided may map tothe force detected by a force sensor that measures the force actingbetween the jaws of the end effector. The motor can then be driven withthe target of achieving that level of force at the sensor 53.

In order to provide accurate and workable levels of force feedback themotor 50 and the gearbox 51 must be of sufficient size. This presentspackaging difficulties to fit the motor and/or the gearbox in thecontroller without the controller becoming excessively large. Bydesigning the controller so that the axis 25 a of the trigger can bealigned with the grip of the controller, the motor and gearbox canconveniently be located within the grip. The motor may be wholly, mostlyor partly within the grip. The gearbox may be wholly, mostly or partlywithin the grip. The output of the gearbox may be coincident with theaxis of the trigger. It has been found that this approach has a numberof advantages. First, there is no need for an additional gear mechanismto translate or rotate the drive from the motor to act about the axis ofthe trigger. This reduces weight in the controller and reduces assemblycost. Second, many typical motors and gearboxes suitable for the taskare 10 to 40 mm in diameter. These can readily fit in a grip 24 intendedto be fully or partially encircled by the user's fingers. Third, themotor and gearbox may comprise much of the weight of the controller. Bylocating them within the part of the controller that is gripped by theuser the loading on the user's wrist and hand to support the controllerin a given attitude can be reduced.

The motor and/or the gearbox could be of circular cross-sectionperpendicular to axis 25 a. Axis 25 a could be at the centre of thatcross-section. Alternatively, the axis 25 a, and correspondingly theoutput shaft of the gearbox, could be offset from the cross-sectionalcentre of the motor and/or the gearbox.

In order for the trigger to be directly driven about its rotation axisby the output of the motor 50 or the gearbox 51, the rotation axis ofthe trigger should extend through the grip portion. To illustrate, ifthe rotation axis of the trigger is positioned as shown at 25 b in FIG.3 e it is difficult for it to be driven by directly by a motor in thegrip. Preferably the rotation axis of the trigger is substantiallyparallel with (e.g. within 30°, 20°, 10° or 5° of the principal axis ofthe grip. This provides flexibility over which motors/gearboxes can beused. The grip may be that portion of the controller that can bepartially or fully encircled by any of the second to third fingers of auser when the user's hand is in position on the controller. The grip maybe a portion of the controller having a length of at least 70 mm alongan axis, and a circumference perpendicular to that axis of between 80 mmand 180 mm at all points along the portion. The grip portion may bedesignated by grooves and/or ridges for aligning the fingers of a usercircumferentially of the grip. The principal axis of the grip may be theaxis running centrally through the grip along its longest dimension.

The control unit may be configured to drive the robot 30 in any suitableway in response to movement of the trigger. However, it is preferredthat the control unit is configured to, in response to movement of thetrigger, cause a movable component of an instrument carried by the robotto move relative to a body of that instrument. The movable component maybe or may be part of an end effector. The movable component may be a jawor cutter. There may be two or more movable opposed jaws or cutters inthe end effector. The control unit may be configured to cause both orall of those jaws or cutters to move towards each other in response toactuation of the trigger. The instrument may be a surgical instrument.Instead of moving a movable component in response to the action of thetrigger, the control unit could perform another function: for example,activating a light or a camera. The robot may be a surgical robot.Alternatively, the instrument could be an industrial or other form oftool. The robot could be an industrial robot or a robot for anotherfunction. The body of the instrument could comprise a coupling forreleasable attachment to a robot and an elongate shaft running betweenthe coupling and the end effector.

Where references to a hand of an operator are dependent on the size andrange of motion of the hand, the hand may be considered to be of theaverage size and range of motion for an adult in the United Kingdom.

The applicant hereby discloses in isolation each individual featuredescribed herein and any combination of two or more such features, tothe extent that such features or combinations are capable of beingcarried out based on the present specification as a whole in the lightof the common general knowledge of a person skilled in the art,irrespective of whether such features or combinations of features solveany problems disclosed herein, and without limitation to the scope ofthe claims. The applicant indicates that aspects of the presentinvention may consist of any such individual feature or combination offeatures. In view of the foregoing description it will be evident to aperson skilled in the art that various modifications may be made withinthe scope of the invention.

The invention claimed is:
 1. A user interface device configured tocontrol a robot manipulator having an end effector comprising at leastone movable element, the user interface device comprising: a bodyconfigured to be held by a user, the body comprising an elongate gripportion configured to be gripped by one or more of a user's second tofourth fingers; a head portion attached to the grip portion, whereby,when the grip portion is held in a right hand of the user, a firstfinger of the user extends along a right flank of the head portion and athumb of the user extends along and is in contact with a left flank ofthe head portion; a trigger extending transversely to the direction ofelongation of the grip portion, the trigger being supported by the headportion so as to be configured to rotate relative to the head portionabout a rotation axis being substantially parallel with a principal axisof the grip portion; and a drive mechanism at least partially housed inthe grip portion, the drive mechanism being coupled to the trigger inorder to apply a torque to the trigger to extend the trigger out of theprofile of the head portion away from the central X-Z plane of the headportion.
 2. The user interface device as claimed in claim 1, wherein thebody is configured to be gripped in normal use by a single hand of theuser.
 3. The user interface device as claimed in claim 1, wherein thehead portion defines a recess on the side thereof opposite the trigger,the recess being configured to receive the thumb of a user gripping thegrip portion.
 4. The user interface device as claimed in claim 1,wherein the trigger is located relative to the grip portion forengagement by the first finger of a user gripping the grip portion. 5.The user interface device as claimed in claim 1, wherein the drivemechanism comprises a motor, the majority of the volume of the motorbeing located within the grip portion.
 6. The user interface device asclaimed in claim 5, wherein the rotation axis of the trigger iscoincident with the rotation axis of the motor.
 7. The user interfacedevice as claimed in claim 1, wherein the drive mechanism comprises agearbox, the majority of the volume of the gearbox being located withinthe grip portion.
 8. The user interface device as claimed in claim 1,wherein the drive mechanism terminates in a drive shaft, the drive shaftbeing coincident with the rotation axis of the trigger.
 9. The userinterface device as claimed in claim 8, wherein the trigger is carriedby the drive shaft.
 10. The user interface device as claimed in claim 8,wherein the length of the grip portion along the axis of elongation isgreater than 50 mm.
 11. The user interface device as claimed in claim 1,wherein the grip portion has an axis of elongation and satisfies one orboth of the criteria: (i) a minimum circumference perpendicular to thataxis of 40 mm and (ii) a maximum circumference perpendicular to thataxis of 160 mm.
 12. The user interface device as claimed in claim 1,comprising a position sensor configured to sense the position of thetrigger relative to the body.
 13. The user interface device as claimedin claim 1, comprising a force sensor configured to sense a forceapplied between the trigger and the body.
 14. A robotic manipulatorsystem comprising: the user interface device as claimed in claim 1; arobot manipulator comprising at least one sensor; and a control unitconfigured to control the drive mechanism to provide force feedback bymeans of the trigger to a user of the user interface device independence on a signal received from the at least one sensor.
 15. Therobotic manipulator system as claimed in claim 14, wherein the at leastone sensor is a force sensor configured to detect a force applied to apart of an end effector carried by the robot manipulator.
 16. Therobotic manipulator as claimed in claim 15, wherein the end effector isan end effector of a surgical instrument carried by the robotmanipulator.
 17. The robotic manipulator as claimed in claim 14, whereinthe user interface device further comprises a position sensor configuredto sense the position of the trigger relative to the body; and thecontrol unit is configured to control the motion of a part of the robotmanipulator in dependence on input received from the at least one sensoror the position sensor of the user interface device.
 18. The roboticmanipulator as claimed in claim 17, wherein the control unit isconfigured to control the motion of the part of the end effector independence on input received from the at least one sensor or theposition sensor of the user interface device.